Linear Search, Binary Search and other Searching Techniques

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Join Stack Overflow to learn, share knowledge, and build your career. A linear search looks down a list, one item at a time, without jumping.

In complexity terms this is an O n search - the time taken to search the list gets bigger at the same rate as the list does. A binary search is when you start with the middle of a sorted list, and see whether that's greater than or less than the value you're looking for, which determines whether the value is in the first or second half of the list.

Jump to the half way through the sublist, and compare again etc. This is pretty much how humans typically look up a word in a dictionary although we use better heuristics, obviously - if you're looking for "cat" you don't start off at "M".

In complexity terms this is an O log n search - the number of search operations grows more slowly than the list does, because you're halving the "search space" with each operation. As an example, suppose you were looking for U in an A-Z list of letters index ; we're looking for the value at index Compare list[12] 'M' with 'U': Smaller, look further on.

Think of it as two different ways of finding your way in a phonebook. A linear search is starting at the beginning, reading every name until you find what you're looking for.

A binary serial and binary search methods, on the serial and binary search methods hand, is when you open the book usually in the middleserial and binary search methods at the name on top of the page, and decide if the name you're looking for is bigger or smaller than the one you're looking for. If the name you're looking for is bigger, then you continue searching the upper part of the book in this very fashion.

A linear search works by looking at each element in a list of data until it either finds the target or reaches the end. This results in O n performance on a given list.

A binary search comes with the prerequisite that the data must be sorted. We can leverage this information to decrease the number of items we need to look at to find our target. We know that if we look at a random item in the data let's say the middle item and that item is greater than our target, then all items to the right of that item will also be greater than our target.

This means that we only serial and binary search methods to look at the left part of the data. Basically, each time we search for the target and miss, we can eliminate half of the remaining items.

This gives us a nice O log n time complexity. So you should never sort data just to perform a single binary search later on. But if you will serial and binary search methods performing many searches say at least O log serial and binary search methods searchesit may be worthwhile to sort the data so that you can perform binary searches. You might also consider other data structures such as a hash table in such situations.

A linear search starts at the beginning of a list of values, and checks 1 by 1 in order for the result you are looking for. A binary search starts in the middle of a sorted array, and determines which side if any the value you are looking for is on.

That "half" of the array is then searched again in the same fashion, dividing the results in half by two each time. Make sure to deliberate about whether the win of the quicker binary search is worth the cost of keeping the list sorted to be able to use the binary search. Open the book at the half way point and look at the page. Ask yourself, should this person be to the left or to the right. Repeat this procedure until you find the page where serial and binary search methods entry should be and then either apply the same process to columns, or just search linearly along the names on the page as before.

Linear serial and binary search methods also referred to as sequential search looks at each element serial and binary search methods sequence from the start to see if the desired element is present in the data structure.

When the amount of data is small, this search is fast. Its easy but work needed is in proportion to the amount of data to be searched. Doubling the number of elements will double the time to search if the desired element is not present.

Binary search is efficient for larger array. In this we check the middle element. If the value is bigger that what we are looking for, then look in the first half;otherwise,look in the second half. Repeat this until the desired item is found. The table must be sorted for binary search. It eliminates half the data at each iteration. If we have elements to search, binary search takes about 10 steps, linear search steps. Binary Search finds the middle element of the array. Checks that middle value is greater or lower than the search value.

If it is smaller, it gets the left side of the array and finds the middle element of that part. If it is serial and binary search methods, gets the right part of the array. It loops the operation until it finds the searched value.

Or if there is no value in the array finishes the search. Also you can see visualized information about Linear and Binary Search here: Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site the association bonus does not count.

Would you like to answer one of these unanswered questions instead? Email Sign Up or sign in with Google. What is the difference between Linear search and Binary search? Bill the Lizard k Please read the appropriate sections in your course material which, has hopefully, been selected and prepared by your instructor s.

Failing that, a general wikipedia, c2 or google search can answer may of these sort of questions. A linear search would ask: The binary search would ask: Binary search requires the input data to be sorted; linear search doesn't Binary search requires an ordering comparison; linear search only requires equality comparisons Binary search has complexity O log n ; linear search has complexity O n as discussed earlier Binary search requires random access to the data; linear search only requires sequential access this can be very important - it means a linear search can stream data of arbitrary size.

Jon Skeet k A better analogy would be the serial and binary search methods my number between 1 and game" with responses of "you got it", "too high", or "too low". The dictionary analogy seems fine to me, though it's a better match for interpolation search. Dictionary analogy is better for me Apr 4 '14 at With dictionary approach, the take away is sorting.

So the importantly you must make sure the data is sorted before the binary search is started. If not you will be jumping all over the oceans without finding the value: If you do not mark the already tried ones, this can become worse. So always do the sorting. Some Java based binary search implementation is found here digizol.

Yes, the requirement that the input data is sorted is my first bullet point Mia Clarke 6, 3 41 I would like to add one difference- For linear search values need not to be sorted.

But for serial and binary search methods search the values must be in sorted order. Pick a random name "Lastname, Firstname" and look it up in your phonebook. Time both methods and report back! Prabu - Incorrect - Best case would be 1, worstwith an average of May 4 '09 at Linear Search looks through items until it finds the searched value. O n Example Python Code: O logn Example Python Code: Stack Overflow works best with JavaScript serial and binary search methods.

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This is the simplest kind of searching. It is also called the linear search or sequential search. Searching starts with the first item and then moves to each item in turn until either a match is found or the search reaches the end of the data set with no match found.

A criteria is set up before the search begins. If no match is found, then the process will return the appropriate message. Serial search is fairly simple to code. For example the pseudo-code below shows the algorithm in action. Each item is checked until either a match is found or the loop ends and the 'return 'no match found' is reached.

Good performance over small to medium lists. Computers are now very powerful and so checking potentially every element in the list for a match may not be an issue with lists of moderate length. The list does not need to be in any order. Other algorithms only work because they assume that the list is ordered in a certain way. Serial searching makes no assumption at all about the list so it will work just as well with a randomly arranged list as an ordered list.

Not affected by insertions and deletions. Some algorithms assume the list is ordered in a certain way. So if an item is inserted or deleted, the computer will need to re-order the list before that algorithm can be applied. The overhead of doing this may actually mean that serial searching performs better than other methods. May be too slow over large lists. Computers take a finite amount of time to search each item, So naturally, the longer the list, the longer it will take to search using the serial method.

The worst case being no match found and every item had to be checked. Challenge see if you can find out one extra fact on this topic that we haven't already told you. Click on this link: Revision resources include exam question practice and coursework guides. Topics include network systems, database, data communications, legal issues such as the Data Protection Act, measurement and control, the OSI model along with the ethics and social effects of ICT at work and home.. Serial searching This is the simplest kind of searching.

It is also called the linear search or sequential search Searching starts with the first item and then moves to each item in turn until either a match is found or the search reaches the end of the data set with no match found. Serial searching algorithm Set up the search criteria Examine first item in the data set If there is a match, end the procdure and return the result with 'match found' If no match is found repeat with the next item If the last item is reached and no match is found return 'match not found'.

Advantages Serial search is fairly simple to code. Disadvantages May be too slow over large lists. This speed disadvantage is why other search methods have been developed. Challenge see if you can find out one extra fact on this topic that we haven't already told you Click on this link: